The compound, 4-thiouracil, produced by the novel process of the subject invention has been known since about 1945. It has been described in the literature as an antibacterial, antitumor agent, useful in photographic processes and as a plant growth stimulator. The compound has been prepared in the prior art by chemical means. There is no known prior art which describes the production of 4-thiouracil by a microbiological process.